This invention relates generally to pressure operated relief valves and more particularly concerns a novel pressure seal for a balanced pressure relief valve. In particular, the seal disclosed provides improved relief valve operation by preventing simmering of the valve and leakage.
Heretofore it has been difficult if not impossible to utilize conventional seals such as "O" rings in piston shut-off valve constructions where one end of the closure member and seat are in abutting relationship. With this type of "face" seal, in high pressure service, rapid movement of the closure member away from the seat results in a 90.degree. change in vented product flow subjecting the seal to substantial aerodynamic forces. These forces tend to lift the seal from its retaining groove resulting in either damage to the seal and impaired subsequent operation, or complete removal of the seal and failure of the valve. These forces also impinge abrasive particles against the seal resulting in damage to and eventual destruction of the seal.
Conventional solutions to seal retention under these conditions usually involve use of seals having cross-sections which can be mechanically retained by positive locking devices such as screws, rivets, or other means. These valves, therefore, in addition to requiring specially manufactured seals are somewhat dificult to maintain since seal replacement has become complex.
The method of main or relief valve seal retention disclosed in this application allows the use of a commonly available "O" ring in a configuration which effectively eliminates the aerodynamic forces tending to lift the "O" ring from its sealing position during valve operation.
Prior art relief and/or valve combinations are disclosed in U.S. Pat. Nos. 3,595,263, 3,664,362, 3,512,560 and 3,568,706; however, prior art attempts at using face seals between the piston and the sealing seat in these valves have not been successful due to removal of the seal material by the turbulence of the fluid flow during valve operation. This deterioration or destruction of the seal results in leakage and valve simmering.
Accordingly, in order to prolong the service life of valves employed to relieve excess pressure in large, high pressure vessels, it is desirable to provide a sealing member that is not subject to abrasion from the flowing media and is not custom molded.